Cisco Adaptive Security Appliances (ASA) can help protect one or more networks from intruders and attackers. Connections between these networks can be controlled and monitored by using the robust features that Cisco ASA offers. You can ensure that all traffic from the protected networks to the unprotected networks (and vice versa) passes through the firewall based on the organization's security policies. This chapter focuses on the features available for packet filtering and their implementations.